基于单窗全相位数字滤波器和LMS准则的窗函数设计

Design of Window Function Based on All Phase Digital Filter with Signal Window and LMS

在FIR滤波器的窗函数设计方法中,窗的选择将直接影响滤波器的性能优劣.为了获得好的窗函数以提高滤波器的性能,本文首先给出了一种新结构带双窗全相位数字滤波器结构,经过理论推导得到与其相对应的FIR滤波器结构以及满足线性相位的条件.指出FIR滤波器中的延迟窗是全相位滤波器中前后窗的卷积,针对单窗全相位系统利用LMS准则找到合适的窗函数序列,又给出原理图和程序流程.最后将得到的窗分别运用到单窗和双窗全相位滤波器中,并画出特性曲线,结果表明加窗全相位滤波器不但具有较高的旁瓣衰减,而且又基本消除了通带和阻带内的波纹.

In designing FIR filter with window, how to choose the window takes directly effect on the performance of the filter. In order to explore fine window function to promote the capability of filter, a novel- structured digital filter with dual windows in frequency domain is firstly presented, thereby the corresponding FIR model system and conditions for linear phrase are given. It is pointed out that the delay window in FIR filter is made from the convolution of front and back window of all phase filter. Principle graph and program flow chart based on single window and LMS are given. Finally the gained window is applied to all phase filter both with single and dual windows, the property chart is drawn as well. The experimental results indicate that all phase filter with such window not only achieves higher first side lobe attenuation but also eliminates the ripples in both pass and stop bands.